Non-destructive Approach for the Prediction of pH in Frozen Fish Meat Using Fluorescence Fingerprints in Tandem with Chemometrics

Abstract

The pH of fish muscle is an important index for quality assessment, but the traditional methods using a pH meter and probe/electrode are destructive, time-consuming, and laborious, making them unsuitable for on-line meat-quality monitoring. Hence, an approach of using fluorescence fingerprints (FFs) for the non-destructive prediction of pH in frozen fish fillets was trialled. Sixty-three live horse mackerel (Trachurus japonicus) and spotted mackerel (Scomber australasicus) were freshly harvested, sacrificed instantly, then preserved in ice, filleted, vacuum-packed, and frozen. Subsequently, the FFs of all frozen fillets were recorded using a fibreoptic-equipped fluorescence spectrometer, and the corresponding pH values of the samples were measured. After pre-processing, the masked FFs were modelled using partial least squares regression (PLSR) for the prediction of pH values. The results revealed that the developed method was accurate enough for predicting the pH changes in frozen horse mackerel and spotted mackerel fillets with R2 = 0.71 and R2 = 0.90, respectively. The proposed technique could be utilized as a rapid and non-contact alternative to traditional pH electrodes for the quality monitoring of fish products.

Potential of fluorescence fingerprints for fish meat authentication: Differences in freshness evaluation in white and dark meat at frozen state

“…As ATP, ADP, and IMP concentrations at 0 h obtained from chemical analysis were certainly different from other storage conditions for both types of muscle (Figure 3), they may be exhibited prominent fluorescence characteristics (Bui et al., 2018; Rahman et al., 2019; Shibata et al., 2018) to contribute this PCA score plot. Moreover, pH‐dependent fluorescence was observed (Postnikova & Yumakova, 1991; Rahman et al., 2016, 2022; Wencel et al., 2014), and the variation of pH‐changing patterns between white meat and dark meat (Figure 5) contributed to the differentiation by PCA of FFs.…”

“…White and dark meat from frozen fish chunks were extracted for measuring pH, as described by Rahman et al. (2022). First, subsamples were cut using a rotary saw from the remaining parts of white and dark meat.…”

“…Masking and preprocessing of FFs data were performed according to previous studies (Rahman et al, 2019(Rahman et al, , 2022. Figure 1 depicts the scheme for preprocessing, masking, and multivariate analysis of FFs spectra.…”

“…Fluorescence fingerprints (FFs) have been demonstrated to be a rapid and noninvasive technique to monitor the freshness status of frozen seafood without thawing the meat (Bui et al, 2018;ElMasry et al, 2015ElMasry et al, , 2016Rahman et al, 2019Rahman et al, , 2021Rahman et al, , 2022Shibata et al, 2018). We have previously investigated a method (FFs) to evaluate freshness by using only white meat (Rahman et al, 2019(Rahman et al, , 2022Shibata et al, 2018), which accounts for a high percentage of edible fish meat.…”

“…Fluorescence fingerprints (FFs) have been demonstrated to be a rapid and noninvasive technique to monitor the freshness status of frozen seafood without thawing the meat (Bui et al, 2018;ElMasry et al, 2015ElMasry et al, , 2016Rahman et al, 2019Rahman et al, , 2021Rahman et al, , 2022Shibata et al, 2018). We have previously investigated a method (FFs) to evaluate freshness by using only white meat (Rahman et al, 2019(Rahman et al, , 2022Shibata et al, 2018), which accounts for a high percentage of edible fish meat. Several methods have been proposed to estimate the amount of contaminated dark meat in fishery products based on hemoprotein (myoglobin and hemoglobin) content (Takeda et al, 1980), and a single radial immunodiffusion test using antisera against muscle-specific myosin light chains (Ochiai et al, 2001).…”